Electric lamp base or cap and bonding cement therefor



Sept. 10, 1946.

ELECTRIC LAMP BASE 0R CAP AND BONDING CEMENT THER H. WEBER 2,407,621

EFOR Filed Jan. 11, 1943 lA/l/fA/TOI? Henryk Weber 5) Patented Sept. 10, 1946 ELECTRIC LAMP BASE OR CAP AND BOND- ING CEMENT THEREFOR Henryk Weber, Bedford, England, assignor of two-thirds to Guarant London S. W. 1, Engla y Plastic Caps Limited, nd, a British company Application January 11, 1943, Serial No. 472,057 In Great Britain December 4, 1941 4 Claims.

The present invention relates to electric lamp bases or caps and to cements for the bonding of such bases or caps to lamp envelopes.

Electric lamp bases or caps as at present made usually comprise a tubular metal skirt which is flared outwardly or enlarged in diameter at one end to facilitate attachment to the glass envelope of the lamp and which, after its formation, has an insulator provided with eyelets or contact plates for attachment to the filament leading-in wires secured in the opposite end. In some cases the skirt is provided with external screw threads to facilitate connection to a co-operating socket, and in others with laterally projecting and separately fitted joint pins forming part of a bayonet connection. The manufacture of these bases or caps involves a number of operations, and it is a matter of some difficulty to provide a good bond between the metal skirt and the glass envelope.

Attempts have been made to overcome the disadvantages attendant upon the manufacture of lamp bases or caps as above described including a proposal to manufacture a bayonet type lamp base or cap having the insulator and skirt formed in one piece by moulding the cap from material comprising phenol-formaldehyde synthetic resin and a filler, such as wood meal. These attempts have, however, not met with success for various reasons, but mainly for the reason that the bases o-r caps were found to have insufficient heat resistance and to be liable to crack and/or blister in the process of cementing them to the glass envelopes with the usual cements which can only convert in shorttime at high temperatures, or, alternatively, in non-commercially long time at low temperatures.

An object of the prevent invention is to provide an improved electric lamp base or cap having high heat resistance and which is such that the number of operations required in its manufacture, and consequently the cost of production, is reduced.

With this object in view the present invention provides a moulded electric lamp base or cap formed with the insulator and skirt in one piece, said base being composed of thermo-setting material made by heating together, natural rosin the ingredients of a thermo-setting synthetic resin compatible with natural rosin and a heat-resisting filler. The natural rosin acts as a water expeller enabling the material. of the base or cap to harden for conversion in relatively short time at low temperature.

The amount of natural rosin incorporated in the material may vary-for example, according to the nature of the synthetic resin and/or the nature of the heat-resisting filler employed-and may be up to about 10% of the thermo-setting material. The heat-resisting filler is preferably a heat-resisting mineral filler and is employed in an amount equal to about two-thirds of the amount of synthetic resin employed.

The ingredients are mixed and the moulding operation carried out in a manner similar to that used in moulding other products from synthetic resinous material.

For the bonding of lamp bases or caps as aforesaid to lamp envelopes a cement which will hardenat low temperatures in commercially short baking time is preferably employed. Acement embodying the same ingredients as the thermosetting material from which the base or cap is made, but preferably in slightly different proportions from those of the base or cap, may conveniently be employed for this purpose.

The threads, in the case of a screw-threaded type base or cap, or the oppositely directed joint pins, in the case of a bayonet type base or cap, necessary to permit the base or cap to be secured to a co-operating, socket may be formed in situ on the base or cap during the moulding operation. However, it is preferred to utilize metal joint pins in bayonet type bases or caps, and these pins may either be fixed in position during the moulding operation or subsequently, For example, a single metal pin of sufficient length to project at each side of the base or cap or two short metal pins may be employed. The pin or pins may be fixed in position during the moulding operation or the base or cap may be formed during mouldingfor instance by the use of appropriately formed diesso that the metal pin or pins can be easily fitted thereto subsequent to moulding, for instance by pressing it or them into position with or without drilling. For this purpose the end wall of the base or cap constituting the insulator may be formed on its inner side with one or more grooves, channels or internal sockets to serve as a seating or seatings for the joint pin or pins which can be forced into position readily through the thin skirt of the base or cap. The one or more grooves or channels may be formed by providing the male or positive die with a corresponding projection or projections, and the one or more internal sockets may be formed by providing one or more recesses or channels in the male or positive die. When a single metal pin is used endwise movement thereof when in position may be prevented by providing the pin at each end with means, such as a radial nick, for engagement with the skirt.

Eyelets or contact plates for the lamp filament leading-in wires may be positioned with respect to the insulator during the moulding operation or subsequently as desired. For the purpose of anchoring the eyelets or contact plates on the insulator the insulator may be provided with recesses or depressions into which the metal of the plates may be pressed. If desired each eyelet or plate may be provided with a projection or projections which is/are pressed into the insulator to secure said eyelet or plate more securely to the insulator.

To facilitate attachment of the base or cap to the glass envelope the base or cap may be flared outwardly or enlarged in diameter at the ,end opposite to that at which the insulator is placed.

The following are examples of a suitable thermo-setting material for the base or cap and a suitable cement for carrying out the present invention, viz:

EXAMPLE I Thcrmlo-setting material Per cent Phenol 32 Formaldehyde 32 Natural rosin 1.5 to 2 Heat-resisting mineral filler 25 Curing agent Remainder EXAMPLE II Cement I Per cent Phenol 30 Formaldehyde 30 Natural rosin---" 6 f Heat-resisting mineral filler 24 Curing agent Remainder In the above examples the curing agent employed may be any usual curing agent for phenol formaldehyde, for instance an aldehyde.

Thermo-setting material as hereinbefore de scribed has a low setting temperature which fa cilitates the manufacture of bases or caps therefrom. Moreover, the molded bases or caps have high heat-resisting properties and are not detrimentally affected by the heat to which they are subjected in the process of cementing them to lamp envelopes.

A moulded electric lamp base according to the present invention is illustrated by way of example in the accompanying drawing in which Figure 1 is a perspective view of the base and Figure 2 is a cross sectional view on the line 2--2 of Figure 1.

As shown in the drawing the base is adapted for attachment to a bayonet type socket and is of conventional shape. The skirt is shown at l and the insulator which is moulded in one piece with the skirt is shown at 2. Inside the base are the seating means 3 for the oppositely directed metal pins 4 which project through the skirt I and enable the base to be secured to a co-operating socket by engagement of the pins in the usual bayonet slots in the socket. 5 are contact plates which are seated with a press fit in recesses 6 formed on the insulator 2 during moulding of the base. The leading in wires of the lamp pass through holes 1 and 8 formed in the insulator 2 and contact plates 5 respectively and are soldered or otherwise attached to the contact plates. In

the case of the lamp base illustrated the seating means 3 are moulded in one piece with the skirt l and insulator 2, the metal pins being suitably positioned in the mould prior to the actual moulding operation.

Where the base is intended to have a screw type engagement with its socket, the seating means 3 and pins 4 are omitted and the screw thread or threads are formed on the outside of the skirt by appropriate shaping of the interior of the mould in which the base is formed.

Having described my invention, what I claim and desire to secure by Letters Patent is:

1. A one piece molded electric lamp base with integral insulator and skirt portions of high heat resisting properties not detrimentally affected by the heat to whichthey are subjected in the process of cementing such base toa lamp envelope, said base being formed from athermosetting material obtained by heating together natural rosin. the ingredients of a thermosetting resin compatible with natural rosin, and a heat resisting filler.

2, A one piece molded electric lamp base with integral insulator and skirt portions of high heat resisting properties not detrimentally affected by the heat to which they are subjected in the process of cementing such base to alamp envelope, said base being formed froma thermosetting material obtained by heating together natural rosin,

the ingredients of a thermosetting resin combat ible with natural rosin, and a heat resisting filler, the rosin constituting up to 19% of the reacting constituents.

.3. A one piece molded electric lamp base with integral insulator and skirt portions of high heat resisting properties not detrimentally aifected by the heat to which they are subjected in the process of cementing such base to a lamp envelope, said base being formed from a thermosetting material obtained by heating together natural rosin, henol, formaldehyde, and a heat resisting filler.

4. A one piece molded electric lamp base with integral insulator and skirt portions of high heat resisting properties not detrimentally affected by the heat to which they are subjected in the process of cementing such base to a lamp envelope, said base being formed from a thermosetting material obtained by heating together natural rosin, phenol, formaldehyde, and a heat resisting filler, the amount of rosin comprising up to 10% of the reacting constituents.

HENRYK 

